1. Field of the Invention
The present invention relates to X-ray apparatus and more particulary to novel and improved X-ray apparatus which is readily convertible for operation in conventional radiographic and tomographic modes.
2. Prior Art
In many conventional radiographic studies, a patient lies on the surface of an X-ray table and an X-ray source located above the table body is energized to direct controlled X-ray emission through a selected portion of the patient. X-radiation which has passed through the patient is incident on a film sheet carried in a Bucky or other film tray beneath the table top. The incident radiation exposes the film sheet to form a shadow image of a portion of the patient's anatomy.
In other conventional radiographic studies, the X-ray source is directed substantially horizontally toward a wall mounted film holder. A patient is positioned with his chest or other body portion adjacent the film holder and the source is energized to form a shadow image on a film sheet carried in the holder.
In another diagnostic procedure called tomography, a patient usually lies on the surface of the X-ray table while the X-ray source and the Bucky tray move in opposite directions in spaced paths longitudinal of the table top. During this movement, the source and the Bucky tray essentially pivot as a unit about an imaginary axis extending through an "examination plane" within the patient. The source is rotated during this movement to assure that it remains directed toward the Bucky. The movement causes images from above and below the examination plane to be blurred on the exposed film sheet, leaving as the only discernable information on the film, information from the examination plane.
In a multipurpose X-ray room, the X-ray apparatus must have exceptional flexibility if it is to meet the demands of these varied procedures. In view of the substantial costs involved in equipping and operating an X-ray room it is important that the installation be operated as efficiently as possible with minimum time being devoted to converting the apparatus for use from one type of procedure to another. The set-up time required to convert prior X-ray apparatus from conventional radiographic to tomographic use and vice versa has been unduly lengthy. Moreover, the set-up procedures have been unduly cumbersome and subject to error.
Typical prior apparatus includes a drive bar which interconnects the X-ray source and a film tray to coordinate their movement during tomography. The drive bar is movably supported on a pivot structure located between the source and the film tray. Since the source and the film tray must be movable independently for conventional radiographic procedures, a means of disconnecting the drive bar from one or both of the source and the film tray is provided.
In order to accommodate the increases and decreases in spacing between the source and the film tray which occur when the source and film tray are moved in parallel but opposite directions, the drive bar is provided with extensible ends. Connecting the drive bar ends with the source and film tray during conversion from conventional radiographic to tomographic operating modes necessitates that the extensible drive bar be physically aligned with and connected to other drive components which connect with the source and the film tray. This procedure is frequently cumbersome and time-consuming to effect, and requires a certain degree of strength, patience and coordination.
With some prior X-ray apparatus, the drive bar assembly is physically removed and stored during conventional radiography, and must be repositioned and mechanically interconnected with other drive system components for tomography. This procedure is likewise cumbersome, time-consuming, and subject to error if the drive bar assembly is improperly reconnected.
A further drawback of prior X-ray apparatus is that the drive bar and certain interconnecting linkage are exposed and extend in plain view during operation of the apparatus. The exposure of such components is necessitated both to facilitate access for connection and disconnection of the components, and because if guards were provided encompassing the wide arcs through which the components move, they would be excessive in size and would greatly inhibit freedom of access to a patient positioned on the table top. The exposed operating components are unsightly and pose safety concerns. The drive bar and its interconnecting components are typically located in relatively close proximity to one side of the table top and are found to inhibit ready access to a patient positioned on the table.
Exposed tomographic drive system components additionally present a sanitation problem. X-radiation opaque substances such as barium are frequently administered to a patient's digestive tract during radiography to facilitate diagnosis. Effluents from patients undergoing these procedures may discharge onto the apparatus and in that event must, of course, be cleaned up between procedures. The cleaning of exposed, complex drive system components is time-consuming and difficult.
Operating noise is a practical problem with some prior tomographic apparatus. The drive bar linkages provided on some prior tomographic apparatus together with other components which interconnect and guide the movements of the source and the Bucky tray tend to generate a substantial amount of noise as a tomograph is being produced. The exposed nature of these drive components facilitates the transmission of such noise into the surrounding environment. The sterile, accoustically reflective surfaces commonly found in X-ray rooms do little to attenuate such noise.
Prior tomographic drive systems have included a spaced array of mechanically actuated electrical switching components which are operative as the source and the film tray move during tomography to energize the source within a desired angular range of operation. A problem with this type of source control has been its complexity. Separate pairs of electrical switches have typically been required to define each desired angular range of source operation. If a prior apparatus is provided with a capability for operating the source selectively in 5, 10, 20, and 40 degree ranges of operation, at least eight switches have been provided at spaced locations to control source operation in these ranges.
A further difficulty with many prior apparatus proposals has been their failure to provide a readily discernable and accurate readout of the location of the tomographic examination plane above the table top. Such mechanical indicators, as have been used on prior apparatus, have typically formed a part of the drive arm or its pivotal mounting structure and, as such, have been located behind the X-ray table along the upstanding tower.